Figure 3.

Conversion of progesterone to 20α-hydroxyprogesterone in the human uterus during pregnancy. Conversion of progesterone to 20α-hydroxyprogesterone was determined in cervical (Panel A) and myometrial (Panel B) tissues from nonpregnant women (NP) (n = 5), pregnant women before labor (Preg NIL) (n = 7), and pregnant women after the onset of labor (Preg IL) (n = 5). Decidual tissues from three women before labor were used for comparison (dec). Cervical epithelium was obtained by scraping the endocervical canal, avoiding the underlying stroma or squamous epithelium. Cervical stroma was obtained remote from the endocervical canal. Myometrial tissues were obtained from the lower uterine segment (Lower Ut Seg) or fundus. Steroid 5α-reductase activity was inhibited by 4-MA (10 μm). Cervical and myometrial tissues were incubated with radiolabeled progesterone (30 nm) for 12 and 24 h, respectively. Each value represents the mean ± se of three to seven individual samples performed in duplicate. *, P ≤ 0.01 compared with cervical epithelium, stroma, or myometrium at any gestational condition.